Sprout Manga by Atsuko Nanba

Reality isn't a shoujo manga, and Miku Ikenouchi's friends know that perfectly well. But then again, they are not Miku-chan. The reason for this is that Miku-chan has a boyfriend, a third year, and is content with what she has. But then a chain of events occur which leaves Miku-chan with a rival (for cuteness), her father quitting his job... and a new roommate?